1. Field of the Invention
The invention relates to automated discrete type biochemical analytical systems wherein a reaction cuvette tray is adapted for bidirectional rotational movement, such as to effect and precisely measure zero-order and first order rate reactions and, also, end-point reactions. The bidirectional rotational movement insures a proper repositioning of each of the individual cuvettes supported on such tray at the treatment stations.
2. Description of the Prior Art
In the field of automated biochemical analytical systems, wherein samples are reacted and analyzed in respect of one or more analytes, it is often desirable that the analyses be performed on a selective basis in respect of each sample. Because of the high demand of clinical laboratories, it is required that such systems should provide, in addition to accurate analytical results, a high thru-put and versatility and, also, low reagent consumption to reduce the cost per input test.
Present-day analytical systems may be divided into two categories. One such category includes the continuous-flow analytical systems, such as described in the L. Skeggs et al U.S. Pat. No. 3,241,341 and the W. Smythe et al U.S. Pat. No. 3,479,141, both assigned to a common assignee. In such systems, continuous streams of successive sample segments and reagent are introduced, at properly related flow rates, into the system and passed along an analytical channel, wherein the successive samples are reacted and analyzed in respect of a same analyte. As described, the stream of sample segments can be divided, or split, into a number of aliquot streams, which are directed each along an individual analytical channel to be reacted and analyzed in respect of a particular analyte. The analytical results derived from the analytical channels are thereafter correlated in respect to the patient or source. While such systems as described in the Skeggs et al patent are not selective, in that a fixed battery of analyses are performed, such systems do exhibit an extremely high thru-put and are capable of satisfying the test requirements of large clinical laboratories. However, the Smythe et al patent describes a continuous-flow system of high thru-put, wherein selectivity is obtained by injecting or introducing, on a selective basis and on in-line fashion, precise volumes of reagents to react with successive sample segments flowing in a continuous stream.
The second category includes discrete-type analyzers, wherein properly related volumes of sample and reagent are introduced into a reaction cuvette, the resulting reaction product being measured to determine the concentration of the analyte. Such systems may be adapted to perform a single type of analysis, termed a batch-type system, or to perform different types of analyses in respect of the individual samples. In such systems, a plurality of reaction cuvettes can be formed into an integral reaction tray, for example as described in U.S. application Ser. No. 284,845, filed July 20, 1981 and assigned to a common assignee. Such tray is rotated to advance each cuvette, in turn, between a reagent addition station, a sample addition station, and an analytical or read-out station.
To obtain maximum versatility, discrete-type systems are often adapted to perform different types of analyses, so as to quantitate various analytes of interest present in biological samples. Such types of reactions can be divided into three types. The first type of reaction can be described as a zero-order rate reaction, as performed in respect as aspartate aminotransferase, alkaline phosphatase, etc., wherein the concentration of the reaction product to be measured varies linearly with time. The second type of reaction can be defined as a first-order rate reaction, as performed in respect of urea nitrogen, creatinine, etc., wherein the concentration of the reaction product varies non-linearly with time. The third type of reaction can be defined as an end-point reaction, as performed in respect of glucose, total protein, etc., wherein the reaction goes to completion before measurement. As is appreciated, analyte quantitation in respect of each of such reactions requires that multiple measurements be made, e.g., colorimetrically, of the reaction product. To achieve highly accurate results, therefore, it is essential that such multiple measurements be made in respect of each individual cuvette, whether supported individually or integrally formed in the reaction tray, uncer identical conditions. Unless this is achieved, accuracy of the analytical result is reduced.
Generally, reaction cuvettes used in discrete-type analytical systems are formed of plastic or glass. As each cuvette is located, in turn, at the read-out station, a beam of light of predetermined wavelength, depending upon the analyte to be quantitated, is passed therethrough and along a sight path of controlled length extending through the reaction mixture. Any variation in the thickness or quality of any imperfections or residues on the cuvette walls defining the sight path would materially affect the light transmissive properties of the cuvette. Hence, any misalignment of the individual cuvette during the multiple readings would change the proper relationship of the successive analytical results, or read-outs, with respect to the reference base-line, which is itself determined by a read-out process.
Hence, unless each individual cuvette is precisely repositioned or aligned at the read-out station, the quantitation of the analyte would not be accurate. The present invention positively insures an accurate repositioning or alignment of the cuvettes in a reaction tray at the read-out station, or at any other station or location, whereby successive analyte measurements are made under identical conditions and accuracy of the analyte measurement is insured.